HP-UX HB v13.00 Ch-13 - LVM

HP-UX Handbook – Rev 13.00 Page 34 (of 110)
Chapter 13 LVM
October 29, 2013
# lvdisplay -v /dev/vg01/lvol1 | more
...
...
--- Logical extents ---
LE PV1 PE1 Status 1 LE PV2 PE2 Status 2
0000 /dev/dsk/c0t6d0 0000 current 0000 /dev/dsk/c1t6d0 0000 current
0001 /dev/dsk/c0t6d0 0001 current 0001 /dev/dsk/c1t6d0 0001 current
...
To reduce the mirror (from PV c1t6d0):
# lvreduce –m 0 /dev/vg01/lvol1 /dev/dsk/c1t6d0
ATTENTION: If the LV uses the distributed allocation policy (aka extent based striping)
you need to specify all PVs that you want to remove the mirror copy from. There is
not (yet) an option that lets you specify the PVG as argument to lvreduce but there
will be a LVM commands patch (maybe mid 2002). To check if the LV uses
distributed allocation policy:
# lvdisplay /dev/vgXX/lvXX | grep Allocation
should show “distributed”.
NOTE: Extending a mirrored LV works exactly like extending a non-mirrored LV.
lvextend enlarges both mirror copies. The LV allocation policies strict or PVG-strict
ensure that the mirrors reside on independent disks or PVGs respectively.
Physical Volume Groups - PVGs
If there are multiple host bus adapters (SCSI or fibre channel) available on the system it
is useful in terms of high availablility to have mirror copies located on different adapters.
The strict allocation policy for mirrored LVs guarantees that the mirror copy will not be
placed on the same disk but it could be placed on a disk that is on the same adapter.
The latter case can be avoided by using physical volume groups. A PVG is a subset of
PVs within a VG that can be defined using -p option of vgcreate/vgextend or simply by
creating an ascii file called /etc/lvmpvg.